This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. -HDL are considered to be the initial acceptors of cellular cholesterol and the first step in the reverse cholesterol process, the process where cholesterol is transported from the cellular membrane to the liver to be degraded. The existence in the membrane of cholesterol domains, so-called lipd-rafts will regulate the efflux and the accessibility of the sterol molecules. We studied how this process occurs using LAURDAN GP imaging with 2-photon excitation and as a membrane system in Giant Unilamellar Vesicles and cells.